'This has all the hallmarks of a hoax,' Mary Riddell wrote prophetically in her column two weeks ago on a supposed letter of rejection received from the BBC by Tony Palmer, one of Britain's foremost film-makers. Palmer, angry at the state of arts commissioning in public service broadcasting, had read out the letter to an audience at the Barbican at the premiere of his new film on Ralph Vaughan Williams, a film the BBC apparently felt did not 'fit its remit', but if 'Mr V Williams had an important premiere in the future' he was to let them know. The composer died in 1958.

The Observer devoted most of a page to a news story on the supposed letter and Mary Riddell expanded on it in the Comment pages. Both pieces were careful to give prominence to denials from the BBC that such a letter, full of management-speak about 'maximising the routes to content' and establishing 'the tools that allow shared behaviours', could have possibly come from their arts commissioning department and noted that Palmer had refused to name its supposed author.

The paper also quoted a BBC spokeswoman asserting that the corporation was 'unable to take this letter seriously without seeing it or without being given the name of who sent it'.

Three days after these pieces appeared, a letter arrived from George Entwistle, controller, knowledge commissioning, marked Not for Publication, which prevents me quoting from it but it's fair to say it was a strongly-worded protest.

It has now become apparent that some of the text of the mystery letter had been drawn directly from a speech given by Simon Nelson, the BBC's controller, portfolio and multiplatform, on 27 September 2007, more than a year after Palmer says he received the letter. Here are the words: 'So having looked at our own activity via a lens of find, play and share we came to these conclusions: it is essential that we reconstruct the architecture of bbc.co.uk to increase findability and to do what we need to maximise the routes to content. We must establish the tools to allow shared behaviours - and so harness the power of our audience and the network to make our content.'

I put this to Tony Palmer, who had supplied The Observer with the text of the 'rejection letter'. He told me confidentially who the supposed signatory was but could not account for the letter's similarity to Mr Nelson's speech, made more than a year later. He claimed to have since discovered the identity of its true author - 'a present member of what used to be called the music and arts department, exasperated by what he sees as the BBC's destruction of its heritage and abnegation of its responsibilities as a guardian of our cultural treasures'.

'While I now accept that I might have been set up, I do not accept that the tone of the letter was false. If it is true that some of the phraseology used in that letter is the same as used in a speech by Simon Nelson, I obviously accept that. But this seems to prove my point, namely that this is gibberish, as is Mr Nelson's job description. The BBC, as a public-service broadcaster, is squandering its precious resources on mumbo-jumbo.'

The BBC has said that no record of Palmer's original film proposal exists, and yet Palmer sent me a copy of a letter he had sent to the BBC on 24 January 2005, outlining his plans to make a Vaughan Williams film in time for the 50th anniversary of his death in 2008. No reply was ever received, he said, adding that this was not unusual. In 2003, he had suggested a film on John Osborne and after 12 unreturned phone calls eventually received an unsigned letter telling him the BBC had lost his original proposal.

The Observer reported that in his Barbican address, Palmer had said his film cost 'under £130,000, which is less than Alan Yentob's bonus'. This might have implied that Palmer believed this to be an annual bonus.

He now maintains he was not referring to an annual bonus or any particular year, but to the total bonuses Mr Yentob has received from the BBC, which, he claims, amount to £225,000 - 'almost twice the cost of my film. What possible justification can there be for this in public service broadcasting?'